It is known that the cephalosporin derivatives represented by compound (5) are important intermediates that can readily be transformed into various types of cephalosporin antibiotics, such as cefazolin, cefmetazole, cefamandole, cefotiam, cefmenoxime, ceftriaxone, cefbuperazone, cefuzonam and cefminox. This can be accomplished by a processes such as acylation of the amino group at the 7 position, substitution of the chloromethyl group at the 3 position with an aromatic heterocyclicthiol, and removal of the carboxylic protective group. Therefore, the compound (5) is valued highly in industry.
Chloro compounds are known in the art. Examples are those cited by R. D. G. Cooper (Tetrahedron Lett., 21, 781 (1980)) and by Shigeru Torii and others (Japanese Unexamined Patent Publication Nos. 57-59896, 57-59897, and 59-55888). These examples concern thiazolidine azetidinone derivatives represented by formula (6): ##STR5## The chloro compounds of formula (6) differ from the thiazolidine azetidinone derivatives of the present invention which are a totally new compounds.
Other known chloro derivatives include those shown by Torii, et al. (Japanese Unexamined Patent Publication Nos. 58-85894 and 59-164771). These derivatives are expressed by the general formula (7) below. These derivatives all include a form where the amino groups are protected by acyl groups as shown in formula (7) below: ##STR6## Thus, an extra process of disconnecting this acyl group becomes necessary at the end of the process. The present invention requires no such extra process.